Enhanced asymmetric induction in cycloadditions to bridgehead-chiral vinyl dioxazaborocines
作者:Christopher D Davies、Stephen P Marsden、Elaine S.E Stokes
DOI:10.1016/s0040-4039(00)00571-2
日期:2000.5
Vinyl dioxazaborocines 5 with asymmetric centres on the nitrogen bridgehead substituent have been prepared and assayed in nitrile oxide and nitrone cycloadditions, giving asymmetricinductions of up to 70 and 74% ee, respectively.
Dual Reactivity Pattern of Allenolates “On Water”: The Chemical Basis for Efficient Allenolate-Driven Organocatalytic Systems
作者:David González-Cruz、David Tejedor、Pedro de Armas、Fernando García-Tellado
DOI:10.1002/chem.200700227
日期:2007.6.4
A study of the reactivitypattern associated with zwitterionic allenolates "on water" is reported. This study establishes the chemicalbasis for two organocatalyzed allenolate-driven reaction networks operating "on water". The first one is a chemodifferentiating three building block (ABB') three-component reaction (ABB' 3CR) manifold comprising terminal alkynoates and aldehydes. The manifold produces
Meldrum’sacid has turned out to be a useful ketene equivalent when faced to nitrone dipoles to form various isoxazolidin‐5‐one derivatives under very mild Brønsted base organocatalytic conditions. The first asymmetric version of this original domino anionic formal [3+2] cycloaddition–decarboxylation reaction was demonstrated by means of quinine‐based organocatalysts.